/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.ipc;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.net.SocketFactory;

import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.retry.RetryPolicy;
import org.apache.hadoop.ipc.Client.ConnectionId;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.SecretManager;
import org.apache.hadoop.security.token.TokenIdentifier;

/**
 * An RPC implementation.
 */
@InterfaceStability.Evolving
public interface RpcEngine {

    /**
     * 获取一个本地接口的代理对象,然后在这个代理对象上调用本地接口的方法
     */
    <T> ProtocolProxy<T> getProxy(Class<T> protocol,
                                  long clientVersion, InetSocketAddress addr,
                                  UserGroupInformation ticket, Configuration conf,
                                  SocketFactory factory, int rpcTimeout,
                                  RetryPolicy connectionRetryPolicy) throws IOException;

    /**
     * Construct a client-side proxy object.
     */
    <T> ProtocolProxy<T> getProxy(Class<T> protocol,
                                  long clientVersion, InetSocketAddress addr,
                                  UserGroupInformation ticket, Configuration conf,
                                  SocketFactory factory, int rpcTimeout,
                                  RetryPolicy connectionRetryPolicy,
                                  AtomicBoolean fallbackToSimpleAuth) throws IOException;

    /**
     * 产生一个RPC Server对象,服务器会启动这个Server对象监听从客户端发来的请求
     * Construct a server for a protocol implementation instance.
     *
     * @param protocol            the class of protocol to use
     * @param instance            the instance of protocol whose methods will be called
     * @param conf                the configuration to use
     * @param bindAddress         the address to bind on to listen for connection
     * @param port                the port to listen for connections on
     * @param numHandlers         the number of method handler threads to run
     * @param numReaders          the number of reader threads to run
     * @param queueSizePerHandler the size of the queue per hander thread
     * @param verbose             whether each call should be logged
     * @param secretManager       The secret manager to use to validate incoming requests.
     * @param portRangeConfig     A config parameter that can be used to restrict
     *                            the range of ports used when port is 0 (an ephemeral port)
     * @return The Server instance
     * @throws IOException on any error
     */
    RPC.Server getServer(Class<?> protocol, Object instance, String bindAddress,
                         int port, int numHandlers, int numReaders,
                         int queueSizePerHandler, boolean verbose,
                         Configuration conf,
                         SecretManager<? extends TokenIdentifier> secretManager,
                         String portRangeConfig
    ) throws IOException;

    /**
     * Returns a proxy for ProtocolMetaInfoPB, which uses the given connection
     * id.
     *
     * @param connId,  ConnectionId to be used for the proxy.
     * @param conf,    Configuration.
     * @param factory, Socket factory.
     * @return Proxy object.
     * @throws IOException
     */
    ProtocolProxy<ProtocolMetaInfoPB> getProtocolMetaInfoProxy(
            ConnectionId connId, Configuration conf, SocketFactory factory)
            throws IOException;
}
